The present invention relates to the general technical field of electric cooking appliances having a removable bowl, and concerns particularly electric fryers. The invention relates more particularly to safety devices for such appliances.
In fryers having a removable bowl, the temperature regulation and thermal protection means cannot be fixed to, or in permanent contact with, the bowl. It is therefore known to mount these means in a flexible manner to allow for the removability of the bowl and to assure a good thermal contact with the bowl when it is installed in the appliance. These limitations on the temperature regulation and thermal protection means give rise to significantly greater thermal inertia and temperature drift than in a fryer having a fixed bowl. These limitations also impair performance consistency, or repeatability, from one appliance to another and poorer operating reliability for those means.
In the case of breakdown of the thermostat of the appliance, the thermal protection is provided by a final, or backup, thermal safety element formed, for example, by a thermal fuse or by a resettable safety limiter. This final safety element can also come into play if the appliance should be heated while the bowl is dry or while the bowl contains an insufficient quantity of cooking fat.
When the final safety element comes into play, either as a result of a breakdown in the appliance, or because of negligence on the part of the user, the user is then obliged to have the appliance repaired. When a meltable fuse is provided, it is necessary to replace the fuse at the same time that possible replacement may be needed for the elements that have broken down. Since a final safety element is involved, it is necessary to check out the repair work very carefully after installation of the new fuse. In the case of a resettable safety limiter, it is only necessary to simply reset the limiter at the time of replacement of any elements that have broken down. This simplifies the repair, particularly when it is necessitated by the user's negligence. However, fabrication of the appliance with a resettable thermal limiter is more expensive than with a meltable fuse.
Electric fryers having a removable bowl generally include an outer case whose interior defines a housing for receiving the bowl. It is known to provide such fryers with a device for detecting the presence of the bowl in the housing. Such a device includes an element for sensing the presence of the bowl, the element cooperating with a switch connected to open the circuit which supplies heating current to the heating means of the fryer if the bowl is not present in the housing or if the bowl is not correctly positioned in the housing. However, if the bowl is correctly positioned in the housing, such a device will not prevent the supply of heating current to the heating means if the bowl is empty or if the bowl does not contain a sufficient quantity of cooking fat.
French Patent Document FR2 724 835 describe an electric fryer having a case forming a housing provided to receive a removable bowl, means for heating the bowl and a safety device including an element for sensing the presence of the bowl. The sensing element is mounted to be movable against a restoring, or bias, means between a first position when the bowl is correctly positioned in the housing and a second position when the bowl is not present, or is incorrectly positioned, in the housing. This second position is a position into which the sensing element is urged by the restoring means. The sensing element of the safety device defines a detection zone and an actuation zone. The detection zone is provided to cooperate with the bowl and the actuation zone is provided to cooperate with a switch arranged to close the current supply circuit for the heating means when the sensing element occupies the first position. The switch disconnects the current supply circuit from the heating means when the sensing element occupies the second position. The sensing element can also provide thermal safety by cooperating, by thermal conduction with a safety thermostat. However, the safety thermostat is an additional component.